WPI receives $25 million award from U.S. Army to develop cold spray AM technique

WPI receives $25 million award from U.S. Army to develop cold spray AM technique
Cold spray Additive Manufacturing can be used to perform surface repairs on damaged metal structures (Courtesy Worcester Polytechnic Institute)

Worcester Polytechnic
Institute (WPI), Worcester, Massachusetts, USA, has received a three-year,
$25 million award from the U.S. Army Combat Capabilities Development Command
Army Research Laboratory (CCDC-ARL) to develop cold spray Additive
Manufacturing for use in the repair and production of metal parts.

WPI’s cold spray Additive
Manufacturing process uses a pressurised gas to accelerate metal powders to
near supersonic speeds. The force of impact
causes the powders to adhere to the metal build
surface. The institute explained that the process can be adapted to work with a
portable handheld applicator, making it suitable for use in the military

“The army is interested
in cold spray 3D printing as a repair technique,” stated Danielle Cote,
assistant professor of materials science and engineering and director of WPI’s
Center for Materials Processing Data, and the principal investigator for the
ARL project. “It’s cheaper to repair a part than to replace it, and you
get the equipment back in service faster.”

“The army’s primary
interest is unit readiness,” she continued. “If you’re on a mission
and need to move quickly to a safer place, and a critical part on your vehicle
breaks, you’re stuck unless you can repair it quickly. That’s where cold spray
comes in.”

WPI states that its primary
research focus will include developing, characterising, and testing new alloys
optimised for use in cold spray. Cote explained that the characteristics of the
metal powders used in cold spray are important since the metal is not melted
before being sprayed onto a part that needs repair, nor heat treated after

Cote added, “With most
manufacturing methods, metal alloys are alerted by first being melted, and then
often heat treated to strengthen or otherwise improve their properties. With
cold spray, what you end up with in the repair is exactly what you start with,
so the characteristics of the powders are quite important.”

As part of the research, the
institute will reportedly use a variety of equipment, including instruments
acquired as part of the new ARL award. These include tools to study the
chemical and structural properties of the powders at the scale of nanometers,
such as a SEM/EDS (Scanning Electron Microscope and Energy Dispersive
Spectroscopy) unit, a synchronous laser diffraction and dynamic image particle
analyser to determine powder morphologies, and nanoindenters to measure
nano-scaled mechanical properties.

WPI’s research team plans to work
with several subcontractors, including the University of California Irvine, the
University of Massachusetts Lowell, Penn State University, and Solvus
Global. Among the modifications that are expected to be made to the
powders are unique thermal processing treatments, a technique WPI states that
it pioneered.

Unlike metals used in other
metal manufacturing processing, including casting and forging, the alloys used
in cold spray do not have to be capable of being heat treated, which gives the
WPI researchers access to a wide range of potential materials. However,
the properties of cold spray powders can be fine-tuned with the careful
application of heat. 

Cote further added,
“This expertise is part of the reason the ARL continues to support WPI. We
have discovered that the properties of metal powders can be significantly
enhanced with thermal processing, and that is what we are looking to do with
this new award.”

As part of the research
programme, a team of co-principal investigators from multiple disciplines at
WPI will explore some new applications, including the use of cold spray to
apply copper coatings to give equipment antibacterial
properties. Researchers in WPI’s robotics engineering programme will
explore the use of multi-axis robots to automate the cold spray process. 

Cote continued, “The
army is especially interested in portable cold spray systems, but the
technology can also be used on a larger scale in industry, for example and it
will be exciting to see how robots can help expand the use of this and other
Additive Manufacturing processes.”

“I think there is much
potential for this technique. With the work we will be doing with powder
development, in robotics, and in a number of other areas, I think we are going
to go a long way with cold spray. There really are endless possibilities,”
she concluded.

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